JPH0690507B2 - Photomask, projection exposure method using the same, and method of manufacturing photomask - Google Patents

Description

The present invention relates to a photomask (or reticle) which is an original image of a projection exposure apparatus, and more particularly to a photomask suitable for transferring a fine pattern.

[Conventional technology]

A projection exposure apparatus that illuminates a mask (hereinafter referred to as a reticle) on which an original image pattern is drawn with an illumination system and transfers the pattern on the reticle onto a wafer requires miniaturization of the transferable pattern. The resolution, which indicates how fine a pattern can be transferred by the projection exposure apparatus, is evaluated by whether or not two adjacent bright parts can be separated when the pattern on the reticle is transferred onto the wafer.
It is known that as a method of improving the resolution, a phase difference may be given to the exposure light at two adjacent transmitting portions on the reticle. Conventionally, a reticle pattern that gives a phase difference to exposure light is disclosed in, for example, Japanese Patent Laid-Open No. 58-17.
3744 is mentioned. In the reticle proposed in this conventional example, as shown in FIG. 4, a light shielding portion 2 which is an original image of a pattern is provided on a reticle substrate 1, and a light shielding portion 2 which is an original image of a pattern is further provided thereon, and further, Further, a layer 6 for changing the phase of the exposure light (hereinafter referred to as a phase shift layer) is provided.

[Problems to be solved by the invention]

In the above-mentioned conventional example, in manufacturing a reticle, exposure and etching for forming a light-shielding pattern are required first, and then a step of exposing the phase shift layer pattern in proper alignment with the light-shielding pattern is required. Therefore, two exposure steps are required to manufacture the reticle, the steps are complicated, and the function of changing the phase of the exposure light is deteriorated when an alignment error occurs during pattern exposure of the phase shift layer. There are drawbacks.

An object of the present invention is to solve the above-mentioned problems and to provide a technique for producing a reticle having a structure capable of changing the phase of exposure light of a light-shielding pattern in one exposure step.

[Means for solving problems]

In order to achieve the above object, the present invention has a structure in which the thickness of glass as a reticle substrate is partially different in order to cause a phase difference in exposure light. In manufacturing a reticle, after coating a photoresist on a light-shielding film, an exposure with different exposure energies is partially performed, and an opening portion that reduces the thickness of the glass substrate to generate a phase difference,
A resist pattern having a different thickness is formed on the opening portion that does not change the thickness of the glass substrate. And
By etching the light-shielding film and the glass substrate, dry etching the resist, and etching the light-shielding film in this order, a desired reticle can be provided.

[Action]

According to the configuration of the present invention as described above, a difference is formed in the thickness of the light transmitting portion of the reticle substrate itself, the phase of the transmitted light can be made different based on the above difference, and the thickness of the above The difference can be formed by one exposure light step.

Example of Invention

Hereinafter, the present invention will be described using examples. FIG. 1 is a view showing a cross section of a reticle to which the present invention is applied. Here, the light-shielding film made of Cr has two openings 3-1 and 3-
Taking an example in which five line patterns composed of 2,3-3,3-4,3-5 are formed, a cross section in a direction perpendicular to the longitudinal direction of the line pattern is shown. The illustrated reticle is
It is characterized in that a difference t is given to the thickness of the glass substrate 1 at the opening.

The thickness t of the layer for changing the phase is n, the wavelength of the exposure light is λ. Given in. For example, if quartz glass is used as the material of the layer, n = 1.46, so when λ = 0.365 μm, t =
It becomes 0.397 μm. As shown in FIG. 1, the glass substrate is removed by 0.397 μm from the openings 3-2 and 3-4 at every other opening out of the five openings. Therefore, if this reticle is illuminated from the top with a high degree of coherence,
As shown in FIG. 2, the amplitude distribution of the transmitted light (exposure light) of the reticle is reversed in the sign of the opening having a large thickness with respect to the opening having a thickness of the glass substrate smaller than that of the conventional exposure light. The effect is exactly the same as that of a reticle that changes the phase of.

Next, a procedure for manufacturing the reticle of the present invention will be described with reference to FIG. First, as shown in (A), 800 Å of Cr which is the light shielding film 2 is vapor-deposited on the glass substrate 1. Further, a photoresist 5 is applied on it. Next, the pattern of the opening is exposed. At this time, since the exposure intensity is changed for each pattern, in the resist pattern after the development processing, the pattern portions 3-2 and 3-4 are completely removed as shown in FIG. The resist film thickness of 1,3-3,3-5 is about 1 /
It is only reduced to 2. Here, when Cr is etched with nitric acid and the glass substrate is further etched with diluted hydrofluoric acid, openings 3-2 and 3-4 are formed as shown in (D). Next, the remaining resist is vertically dry-etched to reduce the film thickness.
The resists of 1,3-3 and 3-5 are removed (Fig. 3 (E)).
Etching Cr with nitric acid again gives 5 as shown in (F).
Openings are formed at the places. Finally, all the remaining resist is removed to complete the reticle of the present invention shown in FIG.

〔The invention's effect〕

According to the present invention, since it is not necessary to newly form a layer that causes a phase difference in the exposure light, a pattern can be simultaneously formed on the photoresist by one exposure step. That is, unlike the conventional case, there is no step of newly exposing the phase shift layer according to the light-shielding pattern, and the pattern is not deteriorated due to the alignment error. Therefore, the reticle manufacturing process is simplified and the pattern reliability is improved.

[Brief description of drawings]

1 is a diagram showing a cross section of a reticle of the present invention, FIG. 2 is a diagram showing an amplitude distribution of exposure light after passing through the reticle of the present invention, FIG. 3 is a diagram showing a manufacturing process of the reticle of the present invention, FIG. FIG. 4 is a sectional view of a conventional reticle. 1 ... Glass substrate, 2 ... Light-shielding film, 3-1, 3-5 ... Opening,
4 ... Amplitude distribution after passing through the reticle, 5 ... Phase shift layer,
6 ... Photoresist.

Claims (5)

[Claims] 1. A photomask, which is an original image of a projection exposure apparatus, for transferring a pattern formed on a mask substrate to an object to be exposed, wherein the mask substrate is made of an optically transparent material having a recess, and the recess is formed. A photomask having a pattern in which the first light transmitted through the second light and the second light transmitted through a portion other than the concave portion have a predetermined phase difference. 2. The photomask according to claim 1, wherein the photomask has a pattern in which a light shielding member is partially arranged in a portion other than the concave portion. 3. The photomask according to claim 2, wherein the light shielding member is a pattern in contact with at least one of the recesses. 4. A projection exposure method of exposing a predetermined pattern on a mask substrate to an object to be exposed by using light from a light source above a photomask, wherein the mask substrate is optically transparent with a concave portion. Of the light from the light source, the first light transmitted through the recess, and
A projection exposure method comprising a step of exposing the object to be exposed with the predetermined pattern so that the second light transmitted through a portion other than the recess has a predetermined phase difference. 5. A method of manufacturing a photomask, comprising forming a light-shielding film on a mask substrate, forming a photoresist film on the light-shielding film, forming a predetermined resist pattern, and etching the light-shielding film using the resist pattern as a mask. In the method, a step of exposing the photoresist film with partially different exposure energies and developing, and etching the light-shielding film by using the resist pattern as a mask, and then etching the mask substrate by using the remaining light-shielding film as a mask. A method of manufacturing a photomask, comprising: a step; and a step of etching the film thickness of the photoresist film having the resist pattern.